The present invention relates to a packet shaping device, router, band control device and control method, and more particularly to a packet shaping method and device for performing shaping to the original burst length when burst of a flow consisted of packet strings grows in a communication device (network device), a router for suppressing burst growth, and a packet receiving control method and band control device for the configuring of a packet non-loss network.
When packet strings pass through a packet processor such as a router a phenomenon occurs in which burst of an input flow grows. The burst specifies the maximum packet capacity necessary for storing simultaneously in the buffers. FIG. 27 is a block diagram of a packet processor for explaining burst growth, and FIG. 28 is an explanatory diagram of burst growth. Flows A, B are input into the packet processor through two input lines #11, #12 respectively, and are stored successively in buffers A, B. If the packets of flow A must be priority processed ahead of the packets of flow B, a selector SL, if packets are present in buffer A, reads out and inputs a packet A1 thereof into a processing part PRC where it is subsequently output to an output line #2 as a processed flow A′. If there are no packets present in the buffer A the selector SL reads out and inputs packets B1, B2 from the buffer B into the processing part PRC where it is subsequently output to an output line #2 as a flow B′. The configuration of the output flow C thereof is shown in FIG. 28E. Here, as shown in FIGS. 28A and B, the burst length of the flows A and B is 3 bytes, the burst length of the initial packet B1 of flow B is 3 bytes, and the burst length of next packet B2 is 1 byte.
Provided no processing delays occur, the 3 bytes of the packet A1 of flow A are priority processed and, as shown in FIG. 28C, the flow A′ is sent without delay to the output line #2. On the other hand, the flow B remains in the buffer B until the 3 bytes of the packet A1 of the flow A have been processed whereupon it is then read out and processed and, at a time t7 following the completion of the processing of the 3 bytes of the initial packet B1, the 1 byte data of the second packet B2 is input. Accordingly, the 1 byte data of the packet B2 is continuously processed without delay at the time t7 and, as a result, as shown in FIG. 28D, the burst length of the flow B′ grows from 3 bytes to 4 bytes. Although the length of each of the buffers A, B is 3 bytes, when the flow B′ is input into the next stage processor the next stage device buffer must be 4 bytes.
The increased burst length produces undesirable outcomes that are increase in the buffer capacity of the next stage processor, increase delay time, and increase packet loss rate. The operation for removing burst growth is referred to as packet shaping and, as a hitherto used technique for achieving this, a well-known leaky bucket shaping device has been used. However, the configuration for achieving this necessitates knowledge of the property about the flow such as maximum burst length of the flow and the like and, apart from this, a leaky bucket shaping device is unsuitable for use in a large-scale network because a separate device is required for each single flow.
It should be noted that a technique for increasing operation efficiency in a data communication network by lowering the burst property of the traffic and suppressing the quantity of network resources that should be secured has been disclosed in the background art (see Japanese laid open Patent Application No. JP2002-314594A). However, this technique of the background art is a technique for statistically suppressing burst length and is not a technique for the deterministic or logical suppression of the burst growth generated in a network.
Based on the above, a demand exists for a device able to more efficiently shape (suppress burst growth) the large number of flows handled by a router without knowledge about the properties of each of the flows.
Thereupon, a packet network that transmits packets has been configured by a send host and a receive host, connection means between the send host and receive host, routers, and transmission links. By way of transmission links and routers, the send host sends packets in which a destination address is written on the packet header thereof to the receive host of the destination address. The router reads the destination address for each received packet and determines the next stage router, whereupon the packet is transferred to the next stage router. This operation is repeated as the packet is led from the send host to the receive host. An increase in the delay time of the packet at this time, that is to say, an increase in the time required to send the packet from the send host to the receive host, and packet loss have a bad influence on the quality of the sound and image carried by the packet.
The cause of increased delay time and packet loss is the increased burst length caused by burst growth in the network and, as a result, an increase in buffer capacity, an increase in delay time and an increase in buffer packet loss rate occur in the downstream flow routers in which the growth accumulates.
Based on the above, a demand exists for a router that suppresses burst growth.
In addition, an existing and significant technical subject is the economical guarantee of communication quality QoS (Quality of Service: packet loss rate, delay and so on) of each flow in a large-scale network.
A technique known as Intserv has been hitherto proposed and, in this technique, a required quality guarantee is realized by identifying individual flow for each of the routers of the network. But in Intserv the information of each of the flows must be recorded in each router and, accordingly, with networks of increased size in which there is an increased number of flows, the system is very complex, very expensive, and unsuitable for actual application.
In addition, a technique referred to as Diffserv has also been proposed. This Diffserv involves the classification of the flows into a small number of quality classes as well as implementation of a quality guarantee operation on flows having an identical quality class with the designated class in batches by the routers.
Although, by virtue of the fact that the routers need only record the operation of quality classes, the actualization thereof is simple, because the operation is implemented in batches, quality assurance of individual flows is impossible and the demands of a user cannot be met.
Based on the above, a demand exists for a packet non-loss network in which the QoS of each flow is guaranteed without need for the recording of the data of each flow.
Although, as described above, a demand exists for a packet shaping device and method able to perform the efficient shaping (suppression of burst growth) of a large number of flows handled by routers without knowledge about the properties of each flow, no such packet shaping device and shaping method are currently available.
In addition, although a demand exists for the economical guarantee of the QoS of each flow in a large-scale network, no such effective technique is currently available. One of the reasons for the generation of the QoS problem is the packet loss produced by buffer overflow that occurs in a router when a flow passes through a router. When the buffer capacity of a router is smaller than the burst length of the flow that is input, that is to say, smaller than the length of the longest packet string that must be simultaneously stored in the buffer of the router, packet discarding and packet loss occur. In order to prevent packet discarding the burst length for each flow must be predicted and the router buffer arrangement must be performed in advance.
However, growth of burst occurs each time a flow passes through a router (burst length at time of output is larger than at time of input). In the relay of a single flow the downstream routers require a successively larger buffer. By virtue of the fact that prediction of growth is difficult, existing IP networks are designed on the premise that packet discarding occurs in the routers. Thereupon, if packet discarding can be prevented in all routers within a network, the desired QoS assurance for each flow-becomes possible in this network.